Method and apparatus for containing a liquified gas



Jan. 24 1961 H. L. JOHNSTON 2,959,092

METHOD AND APPARATUS FOR CONTAINING A LIQUIFIED GAS Filed 001: 21, 19552 Sheets-Sheet 1 we f M? INVENTOR.

giTTQQA/EKS' 2 Sheets-S heet 2 H. L. JOHNSTON W K .m G A m Y 4n H u w Qm U H h METHOD AND APPARATUS FOR CONTAINING A LIQUIFIED GAS HEAT FLOVS.AT FDR VA RIOUS INS LA R5 IN HIGH VACUUM O INTS OBTAINED WITH LIQUIAIR Jan. 24, 1961 Filed Oct. 21., 1955 28: $1 $2 28 3m Em:

320 A INTS OBTAINED METHOD AND APPARATUS FOR CONTAINING LIQUIFIED GASHerrick L. Johnston, Columbus, Ohio, assignor to Herrick L. Johnston,Inc., Columbus, Ohio, a corporation of Ohio Filed Oct. 21, 1955, Ser.No. 541,983

1 Claim. (Cl. 138-64) The present invention relates to conduits forliquified gases having boiling point temperatures below 273 degreesKelvin at atmospheric pressure and particularly to a novel light weightinsulating wall construction for such apparatus.

In apparatus of this type it is common practice to surround thecontainer or conduit, which directly contacts the liquid beingcontained, with a surrounidng wall spaced from the inner container orconduit to form an insulating space. Such insulating space is generallyprovided with insulation consisting of finely divided particles of lowheat conductivity, or such space is connected to a source of vacuum, or,in some instances, both are incorporated. Although such constructionsare thermally efiicient they present the disadvantage of requiringrelatively strong wall constructions and hence have been heavy in weightand relatively expensive to construct.

It has been discovered, according to the present invention, that theabove disadvantages can be eliminated by a novel wall construction whichutilizes insulating material combined with vacuum action to contributeto the structural strength of the wall. Such novel constructioncomprises a relatively thin flexible outer wall member formed ofsuitable thin material such as stainless steel foil. Such outer wallconstruction is combined with an underlying layer of gas-permeableinsulating material, such as cork block or glass fiber blanketing, andby supporting substantially the entire inner surface of the outer wallwith such material, a source of vacuum can be connected to theinsulating space and vacuum created in the interstices of the insulatingmaterial. With this arrangement the thin outer wall of metallic foil isconstantly subjected to an inwardly directed pressure differential whichconstantly urges the thin outer wall against the insulating materialwith the result that such material becomes a structural component of thevessel or conduit and prevents the thin outer wall from collapsing underin the inwardly directed force imposed by atmos- \pheric pressure.Moreover, the insulating material coioperates with the thin outer wallin contributing to the overall strength of the combination since theouter wall is maintained in a structurally desirable designedconfiguration throughout its entire extent whereby such wall means,itself, can most effectively contribute to the structural strength ofthe combination.

As an additional feature of the construction, when the sealed insulatingspace is subjected to a source of low pressure, air is withdrawn fromthe gas-permeable portions of the insulating material to form evacuatedinterstices which contribute to the insulating efficiency of theconstruction.

It is therefore the principal object of the present invention to providea novel insulating wall construction for containing a liquified gaswhich construction incorporates insulating material that contributes tothe structural strength of the construction to provide high insulatingefliciency and strength in a light weight insulatnited States Patent apreferred form of embodiment of the invention is clearly shown.

In the drawing:

Figure 1 of the drawing comprises a view, partially in section, whichillustrates an insulating wall construction for confining a liquifiedgas, said construction being fabricated according to the presentinvention. The section is taken along a vertical plane through andperpendicular to the surface of the wall construction.

Figure 2 is a graph illustrating the rates of radiant heat flow vs.various temperature differences for suitable insulating materialsincorporated in the insulating wall construction of the presentinvention.

Referring next to the drawing, an inner containing means for a liquifiedgas, which containing means may be in the form of a storage chamber orconduit, is indicated generally at 20. Containing means 20 includes aninner wall 21 which directly encloses the liquified gas 22.

The inner wall 21 is surrounded by a thin light-weight outer wall 24formed of metallic foil or the like. As a practical example, stainlesssteel foil of between .010 and .020 inch thickness has been found to besatisfactory.

The outer wall 24 is spaced from the inner wall 21 to provide aninsulating space containing insulating material 25. The insulation 25consists of a suitable gaspermeable material such as cork block or glassfiber blanketing and fills substantially the entire volume of theinsulating space to provide support for the thin metallic foil wall 24throughout substantially the entire inner surface 26 of such wall.

A vacuum line 28 is connected to the insulating space 25 through an endclosure 29 for such insulating space, with the vacuum line 28 leading toa suitable source of low pressure indicated schematically at 30.

According to the present invention air is exhausted from the insulatingspace and from within the interstices of the gas-permeable insulatingmaterial 25 whereby an inwardly directed force, produced by thedifferential between atmospheric pressure and the lower pressure in theinsulating space, constantly urges the metallic foil wall 24 inwardlyagainst insulating material 25. Such inwardly directed force isdiagrammatically represented by the force arrows 32.

The insulating material 25 exerts force outwardly against the innersurface 26 of metallic foil wall 24 as is diagrammatically representedby the force arrows 34.

The outwardly directed arrows 34 are of equal magnitude and oppositelydirected as compared to the inwardly directed arrows 32 since themetallic foil wall 24 is maintained in a designed configuration when theoutwardly directed force 34 exerted by insulating material 25 is inequilibrium with the inwardly directed force 32 exerted by atmosphericpressure.

It will be understood that the light weight outer wall 24 is constructedof such thin material, as compared to the area of its extension, thatsuch outer wall 24 would bow inwardly, or actually collapse, were theoutwardly directed structural support not provided by the insulatingmaterial 25. Hence it is seen that the source of vacuum 30 and theinsulating material 25 cooperate in maintaining the thin outer wall 24in a rigid designed configuration whereby the outer wall 24 can beformed of much thinner, and hence much lighter, material than couldotherwise be used were the insulating material 25 not utilized asstructural support.

Reference is next made to Figure 2 which graphically illustrates radiantheat flow in calories per hour for two insulating materials, in highvacuum, which materials are suitable for the insulating wallconstruction of the present invention. The values on the ordinate of thegraph represent calories per hour and the values on the abscissasrepresent various differences between the fourth powers of the absolutetemperatures T-b and Ts existing on opposite sides of the insulatingmaterial in high vacuum, multiplied by ten to the minus ninth power.

Both cork and glass fiber blanketing represent examples of suitablematerials for the insulating wall construction of the present invention,since these materials provide both structural support and evacuatedinterstices as described herein. It will be noted from the graph,however, that, for any given temperatures T-b and T-s, the heat flow incalories per hour will be less for cork in high vacuum than will be theheat flow through glass fiber blankcting in high vacuum. Both of these,however, provide a lower rate of heat flow than does high vacuum alone.

While the form of embodiment of the present invention as hereindisclosed constitutes a preferred form, it is to be understood thatother forms might be adopted, all coming within the scope of the claimwhich follows.

I claim:

In cryogenics, an insulated conduit construction for a cold liquefiedgas, comprising, in combination, a rigid transfer conduit having aninner surface in contact with said liquefied gas and an outer surfaceexposed to and partially bounding an insulating space, a flexiblecollapsible outer concentric jacket of metallic foil spaced from saidconduit, said jacket having an inner surface bounding said insulatingspace and an outer surface exposed to atmospheric pressure, gaspermeable low temperature insulating material in said insulating spaceand in direct contact with the outer surface of said conduit and theinner surface of said jacket, and means for producing a vacuum in saidinsulating space whereby atmospheric pressure on the outer surface ofthe jacket urges the jacket inwardly so that the insulating materialprovides structural support for the jacket.

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